I've been using a homemade "heat retention cover" (popularly known as "solar cover") and it has been doing its job rather well. My pool water hit 88 degrees the other day! The pool does get 12+ hours of sun during summer months, which obviously helps. I have toyed with whether to leave the cover on during the day or not, and since the plastic I used is "clear" (translucent actually), on a clear day the pool temp increases about as much with the cover left on as it does if I take it off. For this reason, I generally choose to leave the pool covered at all times unless someone wants to swim.
Today I did my weekly chlorine test and decided to measure CC just for kicks and giggles, which I hadn't done in awhile, since the water is clear and CC is always <0.5 when I measure it. I was surprised to find CC=1.0. Should I be concerned and SLAM the pool? The cover was left on today, and I'm wondering if the higher than normal CC could be because the chloramines weren't able to gas off with the pool covered.